Phase equilibrium data for systems composed of oregano essential oil compounds and hydroalcoholic solvents at T = 298.2 K

• (Liquid + liquid) equilibrium data for p-cymene, thymol, terpinen-4-ol, α-terpineol, ethanol and water were determined.
• Complete second order models were fitted to the experimental data.
• Distribution coefficients of thymol, terpinen-4-ol and α-terpineol in pure and mixed solute were evaluated.
• Mass fractions of oxygenated compounds and water influenced the distribution coefficients of the essential oil components.
• NRTL and UNIQUAC thermodynamic models satisfactorily describe the partition of components and solvent selectivity.

The deterpenation process of essential oils consists of terpene removal and a consequent concentration of oxygenated compounds, which increases the sensorial quality, the aromatic potential and the oxidative stability of the oil. Deterpenation of oregano (Origanum vulgare L., Lamiaceae) essential oil, which has been used extensively as a popular medication and as an antimicrobial, antifungal, antimutagenic and a powerful antioxidant agent, can be performed by (liquid + liquid) extraction using hydroalcoholic solvents. This research presents (liquid + liquid) equilibrium data for model systems composed of p-cymene, thymol, terpinen-4-ol and α-terpineol, some of the main components of oregano essential oil, using hydrous ethanol as the solvent with the water mass fraction ranging from 0.28 to 0.41 at T = (298.2 ± 0.1) K. The results show that an increase in the hydration of the alcoholic solvent causes a negative influence on the values of the distribution coefficient for the three oxygenated compounds (thymol, terpinen-4-ol and α-terpineol), with an increase in solvent selectivity. An increase in the content of oxygenated compounds in the terpene-rich phase reduces their distribution coefficients and the selectivity values. In addition, binary interaction parameters were estimated correlating the experimental data using the NRTL and UNIQUAC thermodynamic models, and the global deviations were lower than 0.0060 for all systems, indicating that both molecular models show a good descriptive performance.